Abundance of house dust mites in relation to climate in contrasting agricultural settlements in Israel

The correlation between climatic conditions and mite numbers in houses from rural areas was studied in 13 agricultural communities (kibbutzim and mosh avim) in nine geo-climatic subregions of Israel. Mites were present in 97% of the dust samples. The average number of mites per gram of dust in the di fferent localities ranged between 84 and 2053. The maximum number of mites (7440/g dust) was found in a carpet from a house in Geva Carmel in the nort hern coastal region. The most prevalent species of mites were Dermatophagoi des pteronyssinus and Dermatophagoides farinae, which were found in 85.6% a nd 71.3% of the samples, respectively. The house dust mites D, pteronyssinu s, D, farinae and Euroglyphus maynei constituted 94.8% of the mites. Most o f the mites were isolated from the carpets and sofas (37.0% and 33.7%, resp ectively), and a smaller number from beds (29.3%). The smallest number of m ites (less than or equal to 250/g dust) were found at a minimum relative hu midity (RH) of 30% and lower, with a maximum temperature of 32 degrees C an d higher, i.e. in the Jordan valley and Negev mountains. A greater number o f mites (250-500/g dust) were found at a minimum ambient RH of 35-40% and a maximum temperature of 32 degrees C and higher, i.e, the Hula valley. A la rge number of mites (500-1000/g dust) were found at a minimum RH of 35-40% with a maximum temperature of 30 degrees C and lower, i.e. in the Judean an d Samarian range, as well as in upper Galilee. The largest number of mites (1000-2000/g dust) was found at a minimum RH of 45% and higher, with a maxi mum temperature ranging between 30 and 32 degrees C. These conditions occur in the coastal strip, the coastal plain and in the Judean and Samarian foo thills. A monthly examination of two houses in Zova, a kibbutz in the Judea n hills next to Jerusalem, and two houses from Palmachim, a kibbutz in the coastal region, revealed that the highest prevalence of mites was found in the months April-November and May-November, respectively. In Zova, the high est number of mites were found during the months of June and July while the highest concentrations of D. pteronyssinus-antigen (Der p I) were measured during the month of September. A positive correlation between mite numbers and the quantity of Der p I in house dust was found.